Jeep Wrangler Brakes

j_seph · Apr 18, 2018

Bought this jeep yesterday and noticed the brakes were spongy and would have to pump them to get good pressure to stop. Seems like as long as you are going down the road and press the brake pedal it is a little spongy but works okay. Slow down and pull in somewhere and then hit the brakes it has twice went almost to the floor and basically no brakes unless you pump them. I followed a test I read on the booster and it seems to be functioning properly. Would this be just air in the lines, a leak somewhere, or the Master Cylinder itself causing this?

ryanh487 · Apr 18, 2018

What year? Check the fluid levels. I assume it has rear drums if it's older. Check the rear cylinders for leaks. If there are no obvious leaks, try bleeding the system.

j_seph · Apr 18, 2018

ryanh487 said:
What year? Check the fluid levels. I assume it has rear drums if it's older. Check the rear cylinders for leaks. If there are no obvious leaks, try bleeding the system.

88 model, reservoir is full

paulito · Apr 18, 2018

sounds like what my 89 was doing. ended up having to replace all the brake lines as they had/were rusting thru in places and just not holding. Once i replaced them, and new calipers on the front cuz the connections broke off, the brakes have been fine since.

DAVE · Apr 18, 2018

If no leaks you have a failing master cylinder.

RedRyder · Apr 18, 2018

Try wranglerforum.com in the YJ section. A lot of Jeep folks with years of experience there.

And remember:
J-Just
E-Empty
E-Entire
P-Pocket

Love my Jeep but there is always something to do on it.

ryanh487 · Apr 18, 2018

If the pedal goes to the floor with no resistance there is air somewhere. You said you just got it yesterday, so keep an eye on the fluid over the next few days. Or pump the brakes a lot while it's parked and check for any dribbles or leaks around the back tires or anywhere else. It's possible the seller topped it off right before meeting you and the leak will make itself apparent soon.

Eudora · Apr 20, 2018

My guess would be brake hoses. Have someone press the brake pedal (or as we say around here, "mash down on it") and look to see if the rubber brake hose is swelling. Good luck

transfixer · Apr 20, 2018

Unless the master cylinder looks like its been replaced before, I'd go ahead and replace it, look in the bottom of the reservoir for black material, stick your finger in there if you can ,all the way to the bottom, and if you get black stuff on your finger you can assume the seals are deteriorating . I never trust someone elses brake work, I'd look for leaks at all the wheel cylinders/calipers, and replace as needed, inspect the steel lines for corrosion and the rubber lines as someone else suggested.

NE GA Pappy · Apr 20, 2018

DAVE said:
If no leaks you have a failing master cylinder.

bingo... we have a winner

rayjay · Apr 21, 2018

Just bleed them before doing anything else. That's all it sounds like to me. If the MC is bad it don't pump up and hold. It always sinks down. When you have a small amount of air in the system it will pump up and give a higher pedal until you let off for a few seconds.

Still, you should look for leaks or other issues. On a used vehicle you should pull the wheels and rear drums for a look see and ditto for the front brakes. Brakes are nothing to fool around with and simple to fix. Just throw new parts at it !!!! I just put new calipers and pads on my Dodge 2500 van yesterday.

rayjay · Apr 21, 2018

I may not have been emphatic enough in my warning - you should not be driving this vehicle until you fix it.

7Mag Hunter · Apr 22, 2018

Bleed all 4 wheels till u have clear fluid out of each.....3-4 cycles on each wheel to ensure line is clear of any air bubbles...
also check any rubber lines for rot or swelling...only replace parts after you have a good diagnosis as to what the problem is..

No point in replacing master cylinder if u have a smaller problem..If u replace MS first, u still have to bleed all 4 wheels....
why not bleed first to ensure no simple air bubble problem..

j_seph · Apr 23, 2018

RedRyder said:
Try wranglerforum.com in the YJ section. A lot of Jeep folks with years of experience there.

And remember:
J-Just
E-Empty
E-Entire
P-Pocket

Love my Jeep but there is always something to do on it.

Replaced MC, bleed all brakes except drivers side front and could not get it loose. There was a skim of black dark brown looking gunk in existing MC. Seemed to work fine at initial drive afterwards. Then noticed Saturday the problem came back just not as aggressively. But worse thing is it started making a noise and sounds almost like the exhaust is coming straight out side of engine and acts like it is not firing on all 6 now with a significant loss of power under a load. It is full of oil, compression check on cooling system was perfect. So now onto trying to figure this out and hope it is something simple. Seriously considering just changing out all brake lines and front calipers as well since it may be sitting a little while.

NE GA Pappy · Apr 23, 2018

j_seph said:
Replaced MC, bleed all brakes except drivers side front and could not get it loose. There was a skim of black dark brown looking gunk in existing MC. Seemed to work fine at initial drive afterwards. Then noticed Saturday the problem came back just not as aggressively. But worse thing is it started making a noise and sounds almost like the exhaust is coming straight out side of engine and acts like it is not firing on all 6 now with a significant loss of power under a load. It is full of oil, compression check on cooling system was perfect. So now onto trying to figure this out and hope it is something simple. Seriously considering just changing out all brake lines and front calipers as well since it may be sitting a little while.

if you can't bleed the left front caliper, jerk that sucker off and replace it. You have to make sure all the air trapped in the system is removed. If that bleeder won't come open, then the caliper will have to be replaced.

The engine miss could be a vaccum leak. Since you were working around the brake booster, I would check it closely to make sure you didn't knock a line loose, or crack a brittle vacumm hose.

Eudora · Apr 23, 2018

Long shot, but might remove the vacuum valve on the booster and stick your finger down in there an see if you feel brake fluid. Seen this once where the back of the MC was leaking into the power booster. When it filled up , brake fluid was being pulled into the intake via vacuum and causing a misfire. Worth a check?

Jeep Wrangler Brakes

j_seph

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ryanh487

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j_seph

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paulito

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DAVE

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RedRyder

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ryanh487

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Eudora

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transfixer

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NE GA Pappy

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rayjay

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rayjay

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7Mag Hunter

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j_seph

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NE GA Pappy

Mr. Pappy

Eudora

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